Excessive sleepiness is usually a sign that you aren’t getting enough deep and REM sleep – the sleep stages necessary for feeling rested and healthy.

NREM stage 3 (deep sleep) is the most crucial sleep stage for feeling rested because it is during this stage that brain waves slow down.

In deep sleep, the neuropathways in your brain form at an enhanced rate, enhancing your ability to form memories and store information.

Your brain cycles through four sleep stages, but if you don’t get enough deep and REM sleep, you will be stuck between stages 1 and 2.

While 50% of sleep is spent in NREM stage 2, the brain remains active, emitting high amplitude brain waves similar to when awake. This means you don’t get meaningful rest, and your brain can’t flush toxins.

Here’s why you have excessive sleepiness:

Not getting enough deep sleep

NREM stage 3 lasts around forty minutes but your brain cycles through it during sleep, emitting various brain waves. Neural pathways form and rejig, helping you store information and consolidate memory, and your body releases growth hormone, building and repairing muscles, bones, tissue, and immunity.

If you don’t get enough deep sleep, you will have excessive sleepiness during the day and struggle to function normally.

During NREM stage 2, your brain can’t form the neural pathways necessary for conducting essential neural maintenance. Additionally, musculoskeletal and nervous system repairs cannot be performed efficiently, reducing your ability to recover from injury.

Waking up feeling exhausted and achy is a clear sign you are not getting enough deep sleep, and you should look for ways to sleep better.

Not getting enough REM sleep

REM sleep is different from deep sleep because your brain is highly active, emitting brain waves similar to those when awake. The purpose of REM sleep is brain health, which plays a critical role in memory, emotion, brain development, and maintenance, including eradicating toxins that build up during the day.

If you don’t get enough REM sleep, you can feel muggy and struggle to concentrate, with a noticeable drop in cognitive performance.

Excessive sleepiness is a symptom of inadequate REM sleep as your brain fights against you to fall into slumber and enter recovery mode.

Because REM sleep follows deep sleep and your brain cycles through it, it can happen several hours after nodding off. This is bad news for new parents and those who struggle to stay asleep - the potential for no REM sleep is real!

Not getting enough sleep (full stop)

While deep sleep and REM sleep are critical to feeling refreshed and healthy, they don’t happen without stages one and two.

Stage one transitions you to stage two, where the brain produces rapid bursts of rhythmic brainwaves linked to memory. Your body starts slowing down and preparing you for NREM stage 3, so an interruption here can stop you from getting good sleep.

Healthy adults need between seven and nine hours of sleep every night, which includes an adequate amount of all sleep stages.

Of course, you can’t control what your brain does on autopilot, but you can take steps to minimise the risk of being woken up.

How to get enough sleep and beat sleepiness

A lack of high-quality sleep causes excessive sleepiness - even if you get enough hours in, if you don’t get enough deep and REM sleep, it’s all in vain!

Here are some top tips to get enough sleep:

• Turn off your smartphone an hour before bedtime – smartphones fuel anxiety, and blue light suppress the release of the sleep hormone melatonin.
• Wear earplugs to drown out ambient noise.
• Stretch before getting into bed to increase flexibility and comfort.
• Buy a mattress that balances support and squishiness so that you have adequate comfort in all sleeping positions (read our mattress guide).
• Beat racing thoughts with cognitive distancing, relaxation exercises, and other handy tricks mentioned in this article.